This invention relates to the field of measuring instruments.
There are numerous applications where it is necessary to ascertain the length of an object quickly and accurately by automated methods, or determine if a target is moving.
As an example of a length measuring application, there exist certain personnel identification devices used in physically secure installations where a person's identity is established by measuring his finger lengths.
Various personnel identification devices operate by use of movable photocells. However, these photocell devices use mechanical linkages which are cumbersome, subject to wear and relatively awkward to calibrate. There are other applications where rapidity of measurement is paramount, where the dimensions have to be accurately determined automatically. But as is well known, mechanical devices are relatively slow, compared to electronic devices, and subject to error. Thus, there is a need for a fast, accurate method to measure the length of objects.
As an additional application, the writing, storage and readout of moving targets constitute one of the more vital areas of research in the field of intrusion detection devices. Although the expertise necessary to construct a ferroelectric imaging device is well known, no attempt has been made to explore solutions for other imaging tasks more closely allied to the military or intrusion detection environment. Namely what is required is a simple, low power, moving target transducer. The fundamental problem in using the ferroelectric as a moving target transducer was in getting a readout of the information without recourse to steerable light beams or other relatively high power, relatively large devices.
Thus a need has been created for a simple, low power method of determining whether a target is moving.
Ferroelectrics have been used in the past as image transducers, but they have relied upon movement of the optical indicatrix of the ferroelectric with polarization, since polarization can be made a function of image intensity.